Salt Pollution of the Middle and Lower Sections of the River Werra (Germany) and Its Impact on Benthic Macroinvertebrates

Limnologica 41 (2011) 113–124 View metadata, citation and similar papers at core.ac.uk brought to you by CORE Contents lists available at ScienceDirect provided by Elsevier - Publisher Connector Limnologica journal homepage: www.elsevier.de/limno Salt pollution of the middle and lower sections of the river Werra (Germany) and its impact on benthic macroinvertebrates Ulrich Braukmann a,∗, Dirk Böhme b a Universität Kassel, Fachgebiet Gewässerökologie/Gewässerentwicklung, Nordbahnhofstraße 1a, 37231 Witzenhausen, Germany b BWWU Büro für Wasserwirtschaft und Umwelt, Blümnerstraße 18, D-04229 Leipzig, Germany article info abstract Article history: In two survey phases (2003 and 2008) organic, nutrient and salt contamination parameters have been Received 22 June 2010 investigated in the lower Werra in order to estimate the importance of these different kinds of pollution Accepted 16 September 2010 for the quality component of macroinvertebrates according to the European Water Framework Directive. The chemical and biological investigations have been carried out comparing a “reference” section with- Keywords: out salt contamination with the salt contaminated section due to the potash mining industry from Vacha Werra organic to Hannoversch Münden close to the mouth of the Werra. The results show that the drastic differences Nutrient between the macroinvertebrate assemblages of the Werra upstream and downstream the salt contami- Salt contamination Potash mining nated sections are clearly caused by the salt load. The other kinds of chemical impacts are not responsible Chemical for the observed fundamental change within the composition of the benthic invertebrate assemblage. Biological assessment General degradation of stream morphology, indicated by macroinvertebrates, shows a good ecological Macroinvertebrates status for the non-salt-contaminated part of the river and a bad status for the salt contaminated sites of European Water Framework Directive the lower Werra. © 2010 Elsevier GmbH. All rights reserved. Introduction and 50◦ Gh for the total water hardness. For the third time the limit was adjusted for total hardness to 65◦ Gh in 1996. A fourth time in The River Werra has been polluted by waste waters with 1998/1999 the limits were fixed again to a higher level of 90◦ Gh extremely high salt concentrations from the potash mining indus- which is permitted up to now. try between the Thuringean sampling sites Vacha and Gerstungen Both the extremely high salt load as permitted and the specific for more than 100 years. This salt contamination has continued up salt composition, differing significantly from natural ionic compo- to now downstream not only to the Hessian section of the Lower sition of riverine or estuary waters, form a specific situation among Werra but also to the river Weser until its mouth. the rivers not only in Germany but also in central Europe. The saline At the beginning of the 20th century the potash mining industry pollution leads to a permanent chemical impact on the aquatic emitted salt waste water for the first time in 1901 into the Werra coenoses. (Hübner 2007). Just 10 years later salt pollution caused the first The European Water Framework Directive (EU WFD 2000) clas- problems for the drinking water supply of the city of Bremen. In sifies the ecological status of running waters into 5 quality classes: 1913 a potash commission stated first threshold values for impor- 1 = high, 2 = good, 3 = moderate, 4 = poor, 5 = bad (EU WFD 2000). tant salt water components. For the Werra at the sampling site It demands that natural bodies of water attain a good ecolog- Gerstungen the thresholds for chloride amounted to 842.5 mg/l, ical status by 2015 and heavily modified water bodies a good for total hardness to 48.4◦ German hardness (Gh), for the Weser ecological potential. The ecological status or potential is defined at Bremen to 250 mg/l for chloride and to 20◦ Gh for total hard- by multimetric index systems for the biotic quality components: ness. A first adjustment of these limits to rising amounts of salt fish, macrozoobenthos, macrophytes and phytobenthos (EU WFD effluents took place in 1924 with values of 1781 mg/l chloride and 2000). 63.1◦ Gh at Gerstungen. For the river Weser at Bremen the limits The main objective of this study is to analyse the specific were raised to 350 mg/l for chloride and 23◦ Gh for total hardness. pollution of the Werra and to work out the importance of salt con- A second adjustment fixed a threshold of 2500 mg/l for chloride tamination compared to other anthropogenic impacts. This will be done using the example of the benthic macroinvertebrate commu- nities in the salt polluted section of the Werra, compared to non salt ∗ polluted reference sections of the River Werra and to a naturally Corresponding author. Tel.: +49 5542 98 1632. E-mail address: [email protected] (U. Braukmann). salty stream, the Salzbach near Witzenhausen. 0075-9511/$ – see front matter © 2010 Elsevier GmbH. All rights reserved. doi:10.1016/j.limno.2010.09.003 114 U. Braukmann, D. Böhme / Limnologica 41 (2011) 113–124 Fig. 1. Sampling sites at the River Werra. In a first step, the macrozoobenthos will be evaluated using eco- sections of the Werra have been classified as type 9.2, a large logical metrics according to the German WFD methodology and highland river with a large floodplain (over 300 m wide). All river the results will be related to the saline pollution. Further the ben- sections under study belong to this type. The Salzbach is a small thos data as well as environmental parameters will be analysed tributary of the River Werra near Witzenhausen which may be applying a multivariate approach in order to estimate the relative classified morphologically as a type 7, a small coarse substrate dom- importance of saline pollution, physical habitat, and nutrients for inated calcareous highland stream according to Pottgiesser and the community structure. Sommerhäuser (2004). Its high natural salt concentration results from geological layers of zechstein in its catchment area. Because Study sites of its extremely high salinity the Salzbach stream chemically and biologically represents a special type which is not comparable to The study sites cover the natural geographic regions of the mid- other “regular” streams of type 7. dle and lower section of the River Werra. Based on a German system Fig. 1 shows the position of the actual potash mines and the of stream types (Pottgiesser and Sommerhäuser 2004, 2008) both sampling sites of the sampling periods in 2003 and 2008. U. Braukmann, D. Böhme / Limnologica 41 (2011) 113–124 115 Table 1 Sampling site parameters: site code, mean discharge, distance from source, mean slope of river bed, exposition to saline pollution, sampling frequency in 2003 and 2008. W: River Werra; S: creek Salzbach. Site code Sampling site Distance from Slope of river bed Mean discharge Exposition to salt Sampling Sampling source [km] [‰] [m3/s] pollution frequency 2003 frequency 2008 Chemistry Biology Chemistry Biology W01 Breitungen 101 0.85 21.1 No 2 1 W02 Barchfeld 106 0.80 21.2 No 4 3 2 1 W03 Bad Salzungen 113 0.20 21.5 No 1 W04 Vacha 129 0.35 22.1 Yes 1 W05 Harnrode 137 1.49 28.3 Yes 1 W06 Widdershausen 145 0.35 29.1 Yes 1 W07 Gerstungen 158 0.45 31.0 Yes 4 3 2 1 W08 Hörschel 174 0.36 35.0 Yes 1 W09 Frieda 232 0.69 41.4 Yes 6 3 1 W10 Niederhone 243 0.65 43.2 Yes 6 3 1 W11 Albungen 245 0.70 47.4 Yes 6 3 1 W12 Witzenhausen 275 0.81 49.0 Yes 6 3 1 W13 Blickershausen 282 0.37 50.4 Yes 6 3 2 1 W14 Hann. Münden 297 0.34 51.0 Yes 1 S01 Wendershausen 0,2 79.89 0.01 No 6 3 Methods in salt, the Salzbach, was investigated in order to compare a natural salt water stream with an anthropogenically salinised stream and Sampling design the structure of their benthic invertebrate coenoses. Survey phase 1, 2003 Survey phase 2, 2008 In order to evaluate changes in the zoocoenosis of macroinver- In February and August 2008 a second phase of investigations tebrates by the impact of salt effluents, the Werra was investigated was established in order to rate the actual impact of different pol- in 2003 upstream from the first-known salt contamination area at lutants of the lower Werra downstream. In this phase the impact Barchfeld (Middle Werra). This sampling site is located upstream of different pollutants (organic oxygen consuming waste water from the waste water treatment plant (WWTP) at Bad Salzungen from domestic sources, plant nutrients and salt components) on to avoid influences of domestic sewage. the Werra downstream was studied. In February 11 sites were The sampling site near Gerstungen (Middle Werra) is located investigated by water chemistry analyses regarding the prevail- in the section of the highest salt contamination in this river. The ing point sources of salt contamination as well as the areas of salt immissions originate not only from waste pipes but also from diffuse intrusions of salt into the Werra due to salt disposal into diffuse intrusions of salt waste water from the underground, caused the underground into the “Plattendolomit”. Two sites were estab- by the rising salt enriched groundwater. This salty waste water has lished in the non-salt-polluted segment of the Werra between been anthropogenically pressed into the geological formation of Breitungen and Barchfeld. The 9 other sites reveal the increasing the so called “Plattendolomit”, a special form of zechstein, formerly salt-contamination and the following dilution by the tributaries of believed to be a dense salt-retaining layer several hundred meters the Werra.

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